Conversion between integer and string in C language

There was a need to convert integers to strings , Refer to other great God blogs , Here is a record of , Easy to use at the back .

char* itoa(int value,char*string,int radix);//value:  The integer to convert ,string:  Converted String ,radix:  Convert decimal numbers , Such as 2,8,10,16  Base system, etc 

char* itoa(int num,char* str,int radix)
{
    char index[]="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";// Index table 
    unsigned unum;// Store the absolute value of the integer to be converted , The converted integer may be negative 
    int i=0,j,k;//i Used to indicate the corresponding bit of the set string , After the transformation i It's actually the length of the string ; The order after conversion is reverse , There are positive and negative situations ,k Used to indicate the start of the adjustment sequence ;j Used to indicate the exchange when adjusting the order .
 
    // Get the absolute value of the integer to be converted 
    if(radix==10&&num<0)// To convert to decimal and negative 
    {
        unum=(unsigned)-num;// take num The absolute value of is assigned to unum
        str[i++]='-';// Set to... At the beginning of the string '-' Number , And index plus 1
    }
    else unum=(unsigned)num;// if num Being positive , Directly assign to unum
 
    // Conversion part , Note that the conversion is in reverse order 
    do
    {
        str[i++]=index[unum%(unsigned)radix];// take unum Last digit of , And set to str Corresponding bit , Indicates the index plus 1
        unum/=radix;//unum Get rid of the last one 
 
    }while(unum);// until unum by 0 Exit loop 
 
    str[i]='\0';// Add... At the end of the string '\0' character ,c Language string to '\0' end .
 
    // Adjust the order 
    if(str[0]=='-') k=1;// If it's a negative number , The symbols don't have to be adjusted , Adjust from the back of the symbol 
    else k=0;// It's not a negative number , Everything has to be adjusted 
 
    char temp;// Temporary variable , When you swap two values, you use 
    for(j=k;j<=(i-1)/2;j++)// End to end symmetrical exchange ,i It's actually the length of the string , Index maximum is less than length 1
    {
        temp=str[j];// The header is assigned to a temporary variable 
        str[j]=str[i-1+k-j];// The tail is assigned to the head 
        str[i-1+k-j]=temp;// The value of the temporary variable ( It's actually the previous head value ) To the tail 
    }
 
    return str;// Return the converted String 
 
}

int main(void)
{
    int index = 100;
    unsigned char num[10];
    itoa(index,num,10);
    printf("%s\n",num);
    return 0;
}

Reference blog ：https://www.runoob.com/w3cnote/c-int2str.html